Abstract: A new method was established for monitoring the cytotoxicity of organophosphorus pesticides using mammalian cell line Caco-2 and PC12.Caco-2 cell line was exposed to four organophosphorus pesticides,parathion-methyl,dichlorvos,omethoate and phoxim,at the concentration of 1.0 μmol/L.With the lapse of exposed time,the TEER of Caco-2 declined,and at the time of 60 min,the permeation of Caco-2 exposed to phoxim and parathion-methyl altered distinctly,compared with the control group,being almost 1.5 times higher.The permeation of the four organophosphorus pesticides to Caco-2 was parathion-methyl>phoxim>dichlorvos>omethoate.When the PC12 cell line was exposed to 0.01 μmol/L parathion-methyl and phoxim,the AChE activity declined sharply,but there was no obvious change at higher concentrations.In the omethoate and dichlorvos exposed group,when the concetration was below 1.0 μmol/L,the AChE activity declined laxly,but declined sharply above 1.0 μmol/L.